Thermally processable photosensitive materials forming photographic images with heat development are disclosed in D. Morgan and B. Shely, U.S. Pat. Nos. 3,152,904 and 3,457,075, and D. H. Klisterboer, "Thermally Processed Silver Systems" in Imaging processes and Materials Neblette's Eighth Edition, Edited by J. M. Sturge, V. Walworth and A. Shepp, page 279, 1989.
Such thermally processable materials comprise a reducible silver source (e.g., organic silver salts), a photocatalysts (e.g., silver halides) in a catalytically active amount, and a reducing agent, each of which is generally dispersed in a (an organic) binder matrix. The thermally processable photosensitive materials are stable at ordinary temperature, and after exposure, when they are heated to high temperatures (e.g., at least 80.degree. C.), silver is formed through an oxidation-reduction reaction of the reducible silver source (working as an oxidizing agent) with a reducing agent. The oxidation-reduction reaction is accelerated with a catalytic action of a latent image produced upon exposure. Silver produced by the reaction of an organic silver salt in an exposed area provides a black image. This is in contrast to the unexposed area, and thereby forms an image. Antifoggants are optionally employed to minimize fog in the formed image.
The most effective method as the conventional fog restraining technique was a method in which mercury compounds were employed as antifoggants. Incorporation of mercury compounds as antifoggants in photosensitive materials is disclosed, for example, in U.S. Pat. No. 3,589,903. However, the mercury compounds are not environmentally desired and development of mercury-free antifoggants has been demanded.
U.S. Pat. No. 4,212,937 discloses a technique for reducing fogging and improving raw stock stability the of films by the use of an organic haloamide compound. Any organic haloamide compound which was applied to a laser-exposed and thermally processable photosensitive material, has not been known as yet. Recently, there have been broadly employed thermally processable photosensitive materials for use in medical laser imaging, which is used for infrared semiconductor laser exposure, and thermally processable photosensitive materials containing a contrast-increasing agent and used for outputting of printing image setter having oscillation wavelengths of 600 to 800 nm. When this compound is applied to a thermally processable photosensitive material suitable for laser exposure, it was proved that not only reduced fogging and improved raw stock stability were achieved but also surprisingly superior effects were unexpectedly obtained such that a fog-increase was effectively inhibited during storage of a processed photosensitive material sample.
JP-A Nos. 4-232939, 9-160164, 9-244178, 9-258367, 9-265150, 9-281640 and 9-319022 (herein, the term JP-A means a unexamined and published Japanese Patent Application) disclose a technique for reducing fogging and improving raw stock stability by use of a nitrogen containing heterocyclic compound having a bromine atom pair. Furthermore, JP-A 10-97026 discloses a technique for improving fogging by use of a quaternary polyhalogenated ammonium, a quaternary polyhalogenated phosphonium or a tertiary polyhalogenated sulfonium. However, these compounds were insufficient in improving effects, scarcely having effects in inhibiting a fog-increase during storage of processed samples.